1. Field of Invention
A bi-directional, variable torque output clutch utilizing a ring of spherical members compressed between layers of resilient material.
2. Description of the Prior Art
Conventional clutch devices operate on the principle of sliding friction and consists of a pair of friction discs arranged axially wherein one friction disc is attached to the device input shaft and the opposing friction disc is attached to the output shaft. Various techniques are used to provide a force which presses the two friction discs together. Energization of the driver (motor) results in an angular torque output which is limited by numerous factors including the applied force, coefficient of friction of the discs, etc. In these prior art designs, static-dynamic friction transitions occur, an undesirable characteristic. This is the primary cause for devices which operate on the sliding friction principle tend to skip and chatter and cause uneven start-up operation. Further, sliding friction type devices tend to wear faster than devices based on the concept of rolling friction. A prior art device which improves upon the conventional clutch devices utilizes magnetic particles, such as the model no. CB35DF3, manufactured by Force Limited, Santa Monica, Calif. In this device, clutching and braking functions are provided by the magnetic particles.
Systems in which the magnetic particle clutch device is utilized tend to have problems wherein rapid, braking forces are required. For example, in container inspection systems wherein containers are moved along a conveyor belt and wherein the containers are visually examined to ascertain if the containers are filled, damaged, etc. occasions have arisen wherein the bottles are stopped but the clutch drive is still engaged which causes excessive heat build up inside the clutch. If the condition is sustained for a long time period, the magnetic particles tend to fuse together, effectively damaging the clutch to the point wherein it has to be replaced. The magnetic particle based clutch is also relatively expensive.
In addition, most prior art clutch devices having output torque limiting features typically have one operating torque value. Those devices which provide adjustable torque capabilities tend to be cumbersome, expensive and unreliable.